Synthesis, structure and mesogenic properties of benzoxazole derivatives

Abstract

ABSTRACT Two new homologous series of mesogenic compounds, alkanoic acid 4-{[4-(6-chloro-benzooxazol-2-yl)-phenylimino]-methyl}-3-hydroxy-phenyl ester (3a-c) and alkcanoic acid 4-(6-chloro-benzooxazol-2-yl)-3-hydroxy-phenyl ester (5a-b) incorporating benzoxazole heterocyclic have been prepared and FT-IR, NMR, and MS spectrometry have been used to study the molecular structures. The mesogenic behaviour was examined using POM, DSC, and PXRD (variable temperature) techniques. To evaluate its impact on thermal behaviour and mesomorphic properties, the imine linking group of derivatives was modified and investigated. Enantiotropic SmA is observed by the members of Series-I, while those of series-II show monotropic SmA mesomorphism. These compounds were also examined for their absorption and fluorescent properties. The absorption and photoluminescence spectra of compounds 3a-c occurred at 345 nm and 410 nm, whereas in the case of 5a-b occurred at 325 nm and 370 nm respectively. The GAUSSIAN-09 programme has been utilised to perform DFT calculations at B3LYP level for the purpose of obtaining the stable electronic structures of 3a and 5a.